Article 2 (#1)

First Way:

Our senses prove that some things are in motion. Things move when potential motion becomes actual motion, only an actual motion can convert a potential motion into an actual motion. Nothing can be at once in both actuality and potentiality in the same respect. Nothing can move itself and therefore each thing in motion is moved by something else. It is necessary to arrive at a first mover, put in motion by no other and this everyone understands to be God.

Second Way:

We perceive a series of efficient causes of things in the world. Nothing exists prior to itself therefore nothing is the efficient cause of itself. If a previous efficient cause does not exist neither does the thing that results therefore if the first thing in a series does not exist, nothing in the series exists. The series of efficient causes cannot extend ad infinitum into the past, for then there would be no things existing now. It is necessary to admit a first efficient cause to which everyone gives the name of God.

Third Way:

We find in nature things that are possible to be and not to be, that come into being and go out of being i.e., contingent beings. Assuming that every being is a contingent being, for each contingent being, there is a time it does not exist. It is impossible for these always to exist. Some being exists of its own necessity and does not receive its existence from another being but rather causes them.

Fourth Way:

There is a gradation to be found in things. Some are better or worse than others. Predications of degree require reference to the uttermost case. The maximum in any genus is the cause of all in that genus. Hence there must also be something which is to all beings the cause of their being, goodness, and every other perfection and this we call God.

Fifth Way:

We see that natural bodies work toward some goal and do not do so by chance. Most natural things lack knowledge but as an arrow reaches its target because it is directed by an archer, what lacks intelligence achieves goals by being directed by something intelligence. Some intelligent being exists by whom all natural things are directed to their end and this being we call God.